U.S. patent application number 10/751527 was filed with the patent office on 2005-07-07 for automatic detection of dynamic message sign display panel configuration.
Invention is credited to Zerphy, Bryron L., Zerphy, Eric J..
Application Number | 20050146485 10/751527 |
Document ID | / |
Family ID | 34711447 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050146485 |
Kind Code |
A1 |
Zerphy, Bryron L. ; et
al. |
July 7, 2005 |
Automatic detection of dynamic message sign display panel
configuration
Abstract
In accordance with the invention, there is described systems and
methods for automatically determining the configuration of a sign
display panel. The sign display panel includes a controller
electrically connected to a set of display units by an interconnect
unit. The interconnect unit includes a set of display unit
connection ports for connecting the interconnect unit to a subset
of display units. Each of the display unit connection ports
includes a sensor for indicating whether the subset of display
units is electrically connected to the display unit connection
port. The interconnect unit includes software for automatically
determining the configuration of the display units.
Inventors: |
Zerphy, Bryron L.;
(Macungie, PA) ; Zerphy, Eric J.; (Macungie,
PA) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
34711447 |
Appl. No.: |
10/751527 |
Filed: |
January 6, 2004 |
Current U.S.
Class: |
345/1.1 |
Current CPC
Class: |
G09G 2370/04 20130101;
G06F 3/1431 20130101; G09G 2300/026 20130101; G09G 2380/06
20130101 |
Class at
Publication: |
345/001.1 |
International
Class: |
G09G 005/00 |
Claims
What is claimed is:
1. An interconnect unit for use in conjunction with a sign display
panel, wherein the sign display panel comprises a controller
connected to a set of display units by the interconnect unit, the
interconnect unit comprising: a central processing unit; a set of
display unit connection ports, wherein each of the set of display
unit connection ports is configured for interfacing with a subset
of the set of display units; a sensor corresponding to each of the
set of display unit connection ports for indicating whether the
subset of the set of display units is connected to the each display
unit connection port; and memory for storing interconnect software
configured for execution by the central processing unit, wherein
the software comprises instructions for determining a configuration
of the set of display units.
2. The interconnect unit of claim 1 further comprising a controller
connection port for interfacing with the controller.
3. The interconnect unit of claim 2 wherein the interconnect
software further comprises instructions for sending the
configuration of the set of display units to the controller.
4. The interconnect unit of claim 1, wherein the subset of the set
of display units is connected to each connection port by a
connector.
5. The interconnect unit of claim 4, wherein the sensor comprises
at least one pin at each of the set of connection ports for closing
a switch when the connector is connected.
6. The interconnect unit of claim 1 wherein the instructions for
determining a configuration of the sets of display units comprise
instructions for polling the each display unit connection port to
determine whether the sensor indicates the subset of the set of
display units is connected to the each display unit connection
port, wherein the polling results in a first number representative
of a quantity of the subsets of the set of display units connected
to the interconnect unit.
7. The interconnect unit of claim 6 wherein the instructions for
determining a configuration of the set of display units comprise
instructions for determining a second number representative of a
quantity of the set of display units.
8. The interconnect unit of claim 7, wherein the instructions for
determining the second number comprise sending a message comprising
an integer greater than the second number, the message being
received by each of the set of display units.
9. The interconnect unit of claim 8, wherein each of the set of
display units decrement the integer and the message is returned to
the interconnect unit after each of the set of display units has
decremented the integer
10. The interconnect unit of claim 9, wherein the instructions for
determining the second number comprise determining an amount the
integer was decremented.
11. The interconnect unit of claim 7, wherein the set of display
units is arranged in a matrix of rows and columns and the
instructions for determining a configuration comprise instructions
for determining a total number of columns and a total number of
rows, wherein the total number of rows corresponds to the first
number and the total number of columns corresponds to the second
number divided by the first number.
12. The interconnect unit of claim 6, wherein the instructions for
determining a configuration of the set of display units comprise
instructions for determining a set of row amounts, wherein each row
amount is representative of a quantity of a corresponding subset of
the set of display units.
13. The interconnect unit of claim 12, wherein the instructions for
determining each row amount of the set of row amounts comprise
sending a message comprising an integer greater than the quantity
of the corresponding subset, the message being received by each of
the set of display units.
14. The interconnect unit of claim 13, wherein each of the subset
of the set of display units decrement the integer and the message
is returned to the interconnect unit after each of the subset of
the set of display units has decremented the integer
15. The interconnect unit of claim 14, wherein the instructions for
determining each row amount of the set of row amounts further
comprise determining an amount the integer was decremented.
16. A method for automatically configuring a sign display panel
comprising a set of display units arranged in a matrix of a number
of rows and a number of columns, the method comprising: connecting
the set of display units to an interconnect unit, wherein each row
of the set of display units is connected to a corresponding
connection port of the interconnect unit; detecting each row at the
connection port; determining the number of rows of the set of
display units based on the detected rows; determining a total
number of the set of display units; and dividing the total number
of the set of display units by the number of rows to determine the
number of columns.
17. The method of claim 16, wherein determining a total number of
the set of display units comprises sending a message comprising an
integer greater than the total number of display units to be
received by each of the set of display units.
18. The method of claim 17, wherein determining a total number of
the set of display units further comprises decrementing the integer
at each of the set of display units.
19. The method of claim 18, wherein determining a total number of
the set of display units further comprises receiving the message
after each of the set of display units has decremented the
integer.
20. The method of claim 19, wherein determining a total number of
the set of display units further comprises determining an amount
the integer was decremented.
21. A method for automatically configuring a sign display panel
comprising a set of display units arranged in a set of rows,
wherein each row comprises a subset of the set of display units,
the method comprising: connecting the set of display units to an
interconnect unit, wherein each row of the set of display units is
connected to a corresponding connection port of the interconnect
unit; detecting each row at the connection port; and determining a
total number of the subset of display units for each detected
row.
22. The method of claim 21 wherein determining a total number of
the subset of display units comprises sending a message comprising
an integer greater than the total number of the subset of display
units to be received by each of the subset of display units.
23. The method of claim 22 wherein determining a total number of
the subset of display units further comprises decrementing the
integer at each of the subset of display units.
24. The method of claim 23 wherein determining a total number of
the subset of display units further comprises receiving the message
after each of the subset of display units has decremented the
integer.
25. The method of claim 24 wherein determining a total number of
the subset of display units further comprises determining an amount
the integer was decremented.
26. A system for automatically configuring a sign display panel
comprising a set of display units arranged in a set of rows,
wherein each row comprises a subset of the set of display units,
the system comprising: means for connecting each row of the set of
display units to an interconnect unit; means for detecting each row
connected to the interconnect unit; and means for determining a
configuration of the set of display units, wherein the
configuration comprises a number of rows connected to the
interconnect unit and a number of the subset of display units for
each row.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to sign display panel
communication. More particularly, the present invention relates to
systems and methods for automatically detecting the configuration
of a dynamic message sign display panel.
BACKGROUND OF THE INVENTION
[0002] A dynamic message sign is a sign having a message that can
be changed by a user. Dynamic message signs can be used to publicly
display information that can be changed. For example, dynamic
message signs can be used as roadway signs to alert motorists of
traffic information or they can be used as commercial signs to
advertise business or product information. Dynamic message signs
are typically connected to a controller for controlling the message
on the sign's display. A controller is typically a computer having
a communication interface for communicating with the sign.
[0003] Dynamic message signs can also be made up of multiple
display units, each of which are responsible for producing part of
the sign's display. In a dynamic message sign having multiple
display units, the controller must communicate with each display
unit in order to refresh the display. In order to communicate with
the sign, the controller must recognize the configuration of the
display units. Typically, a user provides the configuration
information to the controller. When the configuration is changed or
the controller is replaced, a user must re-enter the configuration
information.
SUMMARY OF THE INVENTION
[0004] In accordance with the invention, there is described an
interconnect unit for use in conjunction with a dynamic message
sign display panel that automatically determines the configuration
of the sign. The sign display panel includes a controller
electrically connected to a set of display units by the
interconnect unit. The interconnect unit includes a set of display
unit connection ports for connecting the interconnect unit to a
subset of display units. Each of the display unit connection ports
includes a sensor for indicating whether the subset of display
units is electrically connected to the display unit connection
port.
[0005] The interconnect unit includes software for automatically
determining the configuration of the display units. The display
units can be arranged in a matrix of rows and columns where each
row corresponds to the subset of display units and the columns can
be determined by dividing the total number of display units by the
number of rows. In one embodiment the interconnect unit software
can detect the number of display units in each row.
[0006] Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention will
be realized and attained by means of the elements and combinations
particularly pointed out in the appended claims.
[0007] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention, as
claimed.
[0008] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 depicts a block diagram of an exemplary dynamic
message sign display panel, in accordance with systems and methods
consistent with the present invention;
[0010] FIG. 2 depicts a block diagram of an exemplary communication
network for a dynamic message sign display panel, in accordance
with systems and methods consistent with the present invention;
[0011] FIG. 3A depicts a block diagram of an exemplary interconnect
unit, in accordance with systems and methods consistent with the
present invention;
[0012] FIG. 3B depicts a block diagram of an exemplary display unit
connection port, in accordance with systems and methods consistent
with the present invention;
[0013] FIG. 4 depicts a block diagram of an exemplary display unit
for use in a display panel, in accordance with systems and methods
consistent with the present invention;
[0014] FIG. 5 depicts a block diagram of an exemplary controller,
in accordance with systems and methods consistent the present
invention;
[0015] FIG. 6 depicts a flow diagram of an embodiment of a method
for automatic sign configuration, in accordance with methods and
systems consistent with the present invention;
[0016] FIG. 7 depicts a flow diagram of another embodiment of a
method for automatic sign configuration, in accordance with methods
and systems consistent with the present invention;
[0017] FIG. 8 depicts a flow diagram of a method for rapidly
refreshing a sign display panel, in accordance with methods and
systems consistent the present invention; and
[0018] FIG. 9 depicts a flow diagram of a method for error checking
in an exemplary sign display panel communication network, in
accordance with methods and systems consistent with the present
invention.
DETAILED DESCRIPTION
[0019] Reference will now be made in detail to the present
exemplary embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0020] According to the present invention there is disclosed
systems and methods for error detection and correction in a sign
communication system. A dynamic message sign display panel includes
at least one display unit controlled by a controller. The
controller sends a variety of messages to each of the display
units. Each display unit can check each message for communication
errors and also indicate whether there is a break in the
communication network. Furthermore, in one embodiment, the
controller can detect which display unit detected an error in the
message or in the communication network.
[0021] Referring to FIG. 1, there is shown a block diagram of an
exemplary dynamic message sign display panel 100, in accordance
with systems and methods consistent with the present invention.
Sign display panel 100 is made up of a controller 114, a plurality
of display units 110, and an interconnect unit 112. Each of the
display units 110 is responsible for producing patterns on a
portion of the sign display panel 100. In this embodiment, display
units 110 are arranged in a matrix having X number of columns and Y
number of rows. Display units 110 can be arranged in other
configurations and quantities as is understood by those of skill in
the art. The number of columns X and rows Y of the matrix depends
upon the size of the sign display panel 100. FIG. 1 depicts a
display unit 102 in row 1 column 1, a display unit 104 in row 1
column X, a display unit 106 in row Y column 1, and a display unit
108 in row Y column X.
[0022] Display units 110 are controlled by controller 114.
Controller 114 sends messages to and receives response messages
providing feedback from display units 110. In alternative
embodiments, controller 114 may double as a display unit and may
also be responsible for displaying a portion of the sign.
Controller 114 supplies power and data signals to display units 110
and receives data signals from display units 110 through
interconnect unit 112. Controller 114 can be connected to
interconnect 112 by any suitable means for transmitting power and
digital data such as cable or copper wire.
[0023] FIG. 2 depicts a block diagram of an exemplary communication
network for a dynamic sign display panel, in accordance with
systems and methods consistent with the present invention. FIG. 2
depicts each of the display units 110 and the controller 114 of
FIG. 1 as they are connected in the communication network.
Controller 114 and display units 110 communicate with each other in
a directional ring. Accordingly, controller 114 sends information
to display unit 102 in row 1 column 1 and receives information from
display unit 108 in row X column Y. Each display unit receives
information from the display unit in the previous column and sends
information to the display unit in the next column. The final
display unit in a row sends information to the first display unit
in the following row. Thus, display unit 104 in row 1 column X
sends information to the display unit in row 2 column 1 (not
shown). Similarly, display unit 106 in column 1 row Y receives
information from the display unit in column X of the previous row
(not shown) and sends information to the display unit in column 2
row Y (not shown). Finally, display unit 108 in column X row Y
receives information from the display unit in the previous column
of row Y (not shown) and sends information back to controller 114.
In this embodiment, information is sent serially through the
network from the controller 114 to each of the display units 110.
Other embodiment can include networks that send information in
parallel. Display units 110 can be connected to each other by any
suitable means for transmitting power and/or digital data such as
cable or copper wire.
[0024] FIG. 3A depicts the exemplary interconnect 112 of FIG. 1 in
greater detail. The interconnect unit includes a printed circuit
board 300 that includes a controller connection port 302 for
receiving power and data from controller 114 (FIG. 1), and for
sending data to controller 114. Circuit board 300 also includes a
central processing unit (CPU) 306, a memory 308, and a set of
display unit connection ports 304a-304c. In one embodiment, CPU 306
and memory 308 can be combined in a single integrated circuit such
as a microcontroller. Each of the display unit connection ports
304a-304c can provide power to a corresponding row of display units
(not shown), provide data to the display unit in the first column
of the row, and receive data from the display unit in the last
column of the row. Each row of display units is connected to a
corresponding display unit connection port through a connector (not
shown), which may be any suitable means for transmitting power
and/or digital data such as cable, copper wire, fiber optic lines,
or a wireless network. An example of such a connector is Molex
Compodre, which is known and commercially available. Each display
unit connection port includes a sensor for detecting the presence
of a connector.
[0025] FIG. 3B depicts a block diagram of an exemplary display unit
connection port, in accordance with systems and methods consistent
with the present invention. In this embodiment, a display unit
connection port (e.g. port 304a-304c) comprises two pins 320 and
322 for distributing power to the row of display units, two pins
324a and 324b for sending data to the display unit in the first
column, two pins 326a and 326b for receiving data from the display
unit in the last column, two pins 328a and 328b for closing a
switch to indicate the presence of a connector (not shown) that
connects display unit connection port 304a to a row of display
units, and one pin 329 for system reset. The system reset pin 329
provides a means for the controller to issue a restart command to
each display unit in the row of display units independent of the
communication network. In this embodiment, the two pins 328a and
328b, which close the switch, act as the sensor for the connection
port 304a. Alternative sensors, such as a pressure sensor, can be
used as is understood by one of skill in the art.
[0026] Referring to FIG. 3A, CPU 306 executes instructions
associated with interconnect software stored in memory 308. The
interconnect software includes instructions for polling each of the
connection ports (304a-304c) to determine the presence of a
connector at any of the connection ports 304a-304c. For example, if
pins 328a and 328b (FIG. 3B) have closed the switch, the
interconnect software recognizes that a connector has been
connected to connection port 304a. The interconnect software can
send the results to the controller through the controller
connection port 302. As described below, the interconnect software
may also determine the total number of display units and,
therefore, the configuration of the sign.
[0027] FIG. 4 depicts a block diagram of an exemplary display unit
for use in a display panel, in accordance with systems and methods
consistent with the present invention. The display unit includes an
I/O (Input/Output) interface 402 for receiving messages from and
sending messages to another display unit or the controller, a
central processing unit (CPU) 406, read only memory (ROM) 404,
random access memory (RAM) 416, a clock 410, a timer 412, output
drivers 408, and a display output device 414. In one embodiment,
CPU 406, ROM 404, and RAM 416 can be combined in a single
integrated circuit such as a microcontroller, for example Atmel AVR
Microcontroller. The I/O interface 402 can be implemented as RS232C
Transceivers, timer 412 can be implemented as a microcontroller
supervisory circuit, and clock 410 can be implemented as a crystal
oscillator or ceramic resonator. CPU 406 executes instructions
associated with display unit software stored in ROM 404. The
display unit software includes instructions that, when executed,
perform all of the functions associated with operating the display
unit. CPU 406 communicates with the other subsystems of the display
unit over a high speed interconnect or bus 418. RAM 416 stores sets
of display data (or frames) received from the I/O interface 402.
When CPU 406 receives an instruction to refresh the display, CPU
406 processes the frame stored in RAM 416 and sends the process
data to output drivers 408, which refresh display output device
414. Display output device 414 can be any visual display such as an
LED matrix, a liquid crystal display, or a plasma display. In other
embodiments, the display unit can have additional memory and/or
logic for storing a unique address for identification to the
controller.
[0028] FIG. 5 depicts a block diagram of an exemplary controller,
in accordance with systems and methods consistent the present
invention. The controller includes an I/O interface 502 for
receiving data from and sending data to the display units, a
central processing unit (CPU) 504, a read only memory (ROM) 506, a
random access memory (RAM) 507, a user interface 508, a network
interface 510, an environment sensors interface 512, a clock 514,
and a timer 516. In one embodiment, CPU 504, ROM 506, and RAM 507
can be combined in a single integrated circuit such as a
microcontroller. CPU 504 executes instructions associated with
controller software stored in ROM 506 and transmits results to
other subsystems over a high speed interconnect or data bus 518.
The controller software includes instructions that, when executed,
perform functions associated with operating the controller. User
interface 508 is an interface for coupling the controller with
devices such as a keyboard, a mouse, a display device, and any
other I/O device useful in operating and managing the controller as
is understood by one of skill in the art. Network interface 510
communicates with a remote computer over a network (not shown). The
network can be any data communications network including a
combination of networks including the Internet, corporate
intranets, and other networks compatible with a networking protocol
such as TCP/IP. The controller receives input from a user through
the user interface 508 and/or network interface 510. RAM 507 can
store information received from a user. Environment sensors
interface 512 communicates with environment sensors (not shown)
that detect aspects of the environment of the sign display panel
such as temperature, sunlight, or wind speed. The controller can
adjust various aspects of the display according to information
received through the environment sensors interface 512.
[0029] In this embodiment, the controller can transmit three types
of messages: a global message, a local message, and a communication
integrity message. Global messages and local messages can be used
to send data to each display unit, and to instruct each display
unit to update its display. Communication integrity messages can be
used to detect errors in the communication network.
[0030] A global message does not include an address and should be
executed by each display unit that receives it. An example of a
global message is a message to refresh the display. A global
message is typically a single instruction byte that is executed by
the display unit and then sent to the next display unit or, in the
case of the final display unit in the network, back to the
controller. Thus, referring to FIG. 2, controller 114 sends the
global message to the display unit 102. The display unit 102
receives the message from controller 114, executes the message, and
sends the message to the next display unit. Accordingly, each
display unit 110 receives the message from the previous display
unit in the network, processes it, and sends it to the next display
unit until the message has returned to controller 114.
[0031] A local message should be executed by a specific display
unit. For example, local messages typically can be used to provide
each display unit with frames to display. A local message typically
consists of an instruction byte, an address byte, and may also
include one or more data bytes. Before executing a local message,
each display unit checks the address byte. In this embodiment, if
the address is 0, the display unit executes the instruction. If the
address is not 0, the display unit decrements the address and sends
the message to the next display unit in the network. When the
message is received by the appropriate display unit, the address
will be 0 and that display unit will execute the message. In this
embodiment, the address byte is an integer from 0 to N-1, where N
is the total number of display units. For example, referring to
FIG. 2, if the address is 0, display unit 102 will execute the
message. If the address is 1, display unit 102 will decrement the
address and send the message to the next display unit, which will
execute the message because the address will be 0. Likewise, if the
address is 2, display unit 102 will decrement the address, send the
message to the next display unit, which will also decrement the
address, and send the message to the next display unit, which will
execute the message.
[0032] The controller can also transmit a third type of message
called a communication integrity message. The communication
integrity message typically consists of a single byte that is sent
to each display unit. Typically, the controller sends a
communication integrity message to a display unit adjacent to it in
the network, and each display unit sends it to the adjacent display
unit in the network unit the message is received again by the
controller. Thus, the communication integrity message, in one
embodiment, is a single byte instructing each display unit to send
it to the next display unit or back to the controller.
[0033] Using the addressing system associated with local messages,
the controller or the interconnect unit can determine the total
number of display units in a sign display panel. For example,
referring to FIG. 1, interconnect unit 112 can send a local message
having any address value greater than the total number of display
units. Each display unit can decrement the address value and pass
the message to the next display unit. When the address value
returns to interconnect unit 112 from the final display unit in the
panel, the address will be equal to the initial address less the
total number of display units. Thus, interconnect unit 112 can
determine the total number of display units by subtracting the
returned address value from the initial address value. Similarly,
interconnect unit 112 can determine the total number of display
units in each row by reading each address value returned to
interconnect unit 112 from the final display unit in each row.
[0034] Referring to FIG. 6, there is shown a flow diagram depicting
a method for automatic sign configuration, in accordance with
methods and systems consistent with the present invention. The sign
configuration, in one embodiment, can be a matrix of display units
having a number of rows and a number of columns. As described above
with reference to FIGS. 3A and 3B, the interconnect unit includes
software for polling each connection port 304a-304c to determine
the presence of a connector. In this way, the interconnect unit can
detect (step 530) the total number of rows of the display units
because each row corresponds to a connector. The interconnect unit
can determine (step 532) the total number of display units by
sending a local message to each display unit as described above.
Each display unit decrements the address value and the CPU 306 can
receive the address value from the final display unit connection
port after the address value has been decremented by each display
unit. CPU 306, executing instructions from software stored in
memory 308, subtracts the address value received from the final
display unit connection port from the initial address value to
determine the total number of display units.
[0035] Thus, assuming the sign display panel is a matrix where each
row includes the same number of display units, the interconnect
unit or the controller can determine the number of columns in the
matrix by dividing (step 534) the total number of display units by
the total number of rows. For example, referring to FIG. 1, if
interconnect unit 112 determines the total number of display units
110 is 25 and that 5 rows are occupied, the sign display panel must
be a 5.times.5 matrix of display units. Accordingly, controller 114
can receive the configuration of the sign from the interconnect
unit 112 without user input. In other embodiments, controller 112
can determine the total number of display units and, therefore, the
controller 112 can automatically determine the configuration of the
sign display panel based on the number of occupied rows received
from interconnect unit 112.
[0036] Referring to FIG. 7, in another embodiment, the interconnect
unit can determine the configuration of the sign display panel by
polling the connection ports to detect (step 550) each row as
described above, and then determining (step 552) the total number
of display units corresponding to each row. Referring to
interconnect unit 112 depicted in detail in FIG. 3A, CPU 306 can
receive the address value from each display unit connection port
after the address value has been decremented by the display units
in the previous row. CPU 306, executing instructions from software
stored in memory 308, can subtract each such address value from the
address value corresponding to the previous display unit connection
port. For example, display unit connection port 304b returns an
address value to CPU 306 after the address value has been
decremented by each display unit in the row corresponding to
display unit connection port 304a. CPU 306 can subtract the address
value returned from display unit connection port 304b from the
initial address value to determine the total number of display
units in the row of display units corresponding to display unit
connection port 304a. Similarly, CPU 306 can subtract the address
value returned from display unit connection port 304c from the
address value returned from display unit connection port 304b to
determine the number of display units in the row corresponding to
display unit connection port 304b. In this embodiment, the
interconnect unit can send the controller configuration information
consisting of the number of rows and the number of display units
corresponding to each row.
[0037] Using local messages and global messages, a sign display
panel can rapidly refresh itself. FIG. 8 depicts a flow diagram of
a method for rapidly refreshing a sign display panel, in accordance
with methods and systems consistent with the present invention.
FIG. 8 is described with reference to the block diagram of a
display unit depicted in FIG. 4. Local messages can be used to
provide each display unit with sets of display data, or frames, to
display. A frame is typically eight bytes. A frame includes bytes
of data that are processed by the CPU 406 to instruct output
drivers 408 to update the display unit device 414. Output drivers
408 can be, in one embodiment, a series of switches that control a
simple display output device 414, such as an LED display. More
complex output drivers 408 can be used to control a more
sophisticated display output device 414, as is understood by those
of skill in the art. Accordingly, the local message can include one
or more frames along with an instruction to store each frame. In
one embodiment, each frame also includes a frame identifier, which
can be a byte of data such as an integer, that identifies it for
subsequent processing. A display unit can receive the local message
that has been addressed to it as described above. The CPU 406
executes the local message and stores each received frame in RAM
416, which can be large enough to store multiple frames. Thus, each
display unit can receive (step 570) a plurality of local messages,
each containing one or more frames, and store (step 572) each frame
in RAM 416. RAM 416, in one embodiment, can be a standard
first-in-first-out (FIFO) memory.
[0038] The controller can then send a plurality of global messages,
which are received (step 574) by each display unit in series,
instructing each display unit to refresh display output device 414
using the frames in RAM 416. A display instruction can be a single
byte of data that is received by the display unit. The display
instruction, when executed by CPU 406, instructs the display unit
to process one of the frames in RAM 416. In one embodiment, the
display instruction also includes a second byte of data
corresponding to the frame identifier. For example, the second byte
of data can be an integer that corresponds to the integer
identifying the frame. The CPU 406 compares the display instruction
integer to each frame identifier for each frame stored in RAM 416
and then processes (step 576) the corresponding frame. In another
embodiment, the display instruction instructs the display unit to
process the first available frame in RAM 416. In response to each
display instruction, CPU 406 processes (step 576) the frame in RAM
416 identified by the display instruction and sends the results to
the output drivers 408, which update display output device 414.
Thus, each display unit can rapidly refresh its display without the
delay associated with the controller sending additional frames
before sending the instruction to refresh the display.
[0039] Communication integrity messages are used to determine the
communication status of the communication network. Referring to
FIG. 2, controller 114 can periodically send a communication
integrity message to display unit 102. If the controller 114 does
not receive the communication integrity message back from display
unit 108 within a certain amount of time such as, in one
embodiment, 7 seconds, the controller's timer 516 (FIG. 5) sends an
interrupt to its processor. Moreover, in this embodiment, each
display unit can be programmed to send an error message if it does
not receive a communication integrity message for a specified
amount of time. Each display unit includes a timer 412 (FIG. 4)
that sends an interrupt when the communication integrity message
has not been received after a set period of time such as, in one
embodiment, 5 seconds. The interrupt causes the display unit to
send an error message to the next display unit or the controller.
The error message can include an integer, which is decremented by
each display unit that receives it until it is received by the
controller. In this way, the controller can recognize which display
unit first detected the communication error.
[0040] For example, turning to the diagram of FIG. 2, consider a
sign in which there are two rows and two columns of display units.
Thus, the network consists only of controller 114 and display units
102, 104, 106, and 108. If there is a communication error between
display units 102 and 104, display unit 104 sends an error message
to display unit 106 when it has not received a communication
integrity message after the specified amount of time. The error
message can include any integer greater than or equal to N-1, where
N is the total number of display units. In this embodiment, the
controller 114 must be programmed with N or any number greater than
N. Thus, in this example, the integer must be greater than or equal
to 3. Display unit 106 decrements the integer and sends it to the
next display unit. Each display unit that receives the error
message decrements the integer. Thus, controller 114 receives the
error message including the integer. In this example, the integer
has been reduced by 2. Controller 114 can recognize that because
the integer has been reduced by 2, display unit 104, the third to
last display unit, must have sent the error message. Thus,
controller 114 can recognize the communication error between
display units 102 and 104.
[0041] Communication errors may be due to certain temporary
conditions such as a temporary nearby electrical field, or the
presence of water inside one of the display units. Thus, when
controller 114 recognizes a communication error, controller 114 may
perform a diagnostic by resetting the display unit that is causing
the error. If the communication error still exists, controller 114
can shut down the display unit and restart. If the communication
error still exists, controller 114 can shut down the display unit,
wait a period of time such as an hour, and then restart. If the
communication error is still not resolved, controller 114 can be
operated in a supervisory mode that allows a user to test each
display unit to determine the cause of the communication error.
Additional diagnostic utilities can be undertaken as is understood
by those skilled in the art. Because, in this embodiment, each
display unit can report errors detected from a previous display
unit in the communication network, the error checking method does
not depend upon the malfunctioning display unit and is, therefore,
reliable.
[0042] Referring to FIG. 9, there is shown a flow diagram of a
method for error checking in an exemplary sign display panel
communication network, in accordance with methods and systems
consistent with the present invention. The flow diagram will be
described with reference to the block diagram of a display unit
depicted in FIG. 4. First, the display unit waits (step 602) to
receive a byte from another display unit or the controller. If the
byte is not received before timer 412 expires, timer 412 sends
(step 606) an interrupt to CPU 406. Timer 412 can be set to expire
after 7 seconds in one embodiment, and is reset when the display
unit receives a communication integrity message as described below.
Upon receiving the interrupt, CPU 406 sends (step 608) an error
message to the next display unit or to the controller, and CPU 406
can instruct output drivers 408 to clear (step 610) the display
output device 414. An error message is typically a global message
instructing each display unit to clear its display output
device.
[0043] If the byte is received before timer 412 has expired, CPU
406 performs (step 604) a parity check on the received byte. As is
understood by one of skill in the art, the parity check can be even
or odd parity. Each byte includes a parity bit, and CPU 406 checks
the byte to determine if its parity matches the parity bit. If the
received byte fails the parity check (i.e. the parity of the byte
does not match the parity bit), CPU 406 processes (step 612) the
parity error. Processing the parity error can include disposing of
the data, instructing the output drivers 408 to clear the display
output device 414, and sending an error message to the next display
unit or the controller.
[0044] If the received byte does not fail the parity check, CPU 406
determines (step 614) if the byte is a communication integrity
message. In one embodiment, the community message byte includes a
bit that is set if the byte is a communication integrity message.
CPU 406 checks this bit to determine if the received byte is a
communication integrity message. If the byte is a communication
integrity message, CPU 406 resets (step 616) timer 412 to, in one
embodiment, 7 seconds and forwards (step 616) the byte to the next
display unit or to the controller.
[0045] If the byte is not a communication integrity message, CPU
406 determines (step 618) if the byte is a global message. In one
embodiment, the byte includes a bit that is set if the byte is a
global message. CPU 406 checks this bit to determine if the byte is
a global message. If the byte is a global message, the CPU 406
executes (step 620) the global message instruction and sends the
byte to the next display unit or the controller.
[0046] If the byte is not a global message, CPU 406 determines
(step 622) if the byte is part of a local message (i.e. a local
instruction byte, an address byte, or a data byte). In one
embodiment, the byte includes a bit that is set if the byte is part
of a local message. CPU 406 checks this bit to determine if the
byte is part of a local message. If the byte is a local message
byte, CPU 406 determines (step 624) if it has received the entire
message. If not, CPU 406 waits (step 602) to receive additional
bytes. If CPU 406 determines it has received the entire message,
CPU 406 executes (step 626) the message if the address byte is 0.
If the address byte is not 0, CPU 406 decrements (step 626) the
address byte and forwards the message to the next display unit.
[0047] If the byte is not part of a local message, a global
message, or a communication integrity message an error has occurred
and the CPU 406 must process (step 628) the error. This can include
instructing output drivers 408 to clear display unit device 414,
and sending an error message to the next display unit or the
controller.
[0048] As is understood, the error detection protocol of the
present invention can be incorporated with a sign panel
configuration consisting of any number of display units. Also, the
error detection protocol of the present invention can be
incorporated into virtually any sign communication system. For
example, the error detection protocol can be incorporated into a
communication system in which each display unit is assigned an
individual address. In this embodiment, each display unit can
perform an error check of the information received from the
controller and send error messages back to the controller if an
error is detected. Also, the controller can send communication
integrity messages to each display unit, and each display unit can
send an error message back to the controller if the communication
integrity message is not received within a specified period of
time.
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